A knock-down-drag-out fight or argument is an extremely angry or violent one — so wild that you can picture people hitting each other to the floor and dragging them. It is informal, and it is more American than British, though British readers still understand it. You will hear it before nouns: a knock-down-drag-out argument, a knock-down-drag-out battle in court or in politics. Though actually, it is often stretched: nobody needs to be dragged along the ground. It can be all words, just very fierce. It is colourful talk, not a polite or legal term. You may also see knockdown-drag-out or knockdown drag-out; the hyphens wander.